This invention relates to electronic systems and more particularly to self-testing of equipment such as home appliances operated by microprocessor devices.
Most appliances or electronic equipment such as microwave ovens, washing machines, CB radios, TV game devices, automobile ignition controls, and the like are being designed to be controlled by microprocessors. Usually a microprocessor for these purposes is a semiconductor MOS/LSI integrated circuit which has a read only memory (ROM), data storage in the form of a random access memory (RAM), an arithmetic unit for performing calculations or logic functions, and a number of input and output terminals. An example of a processor device of this type is described in detail in U.S. Pat. No. 3,988,604 issued Oct. 26, 1976 to J. H. Raymond, assigned to Texas Instruments. The processor device contains facility for being tested, as a finished part, according to U.S. Pat. No. 3,921,142, assigned to Texas Instruments, but the system itself requires functional testing of each electrical component, either for final test by the manufacturer or for field test by a serviceman. Conventionally, systems test has required various equipment such as volt and ohm meters, oscilloscopes and the like, and can be time consuming and expensive. Testing is further complicated by the fact that solid state control circuitry has few components and thus few terminals are available for probe or for initiating conditions.
It is therefore the principal object of the invention to provide an improved testing arrangement for appliances or electronic equipment. Another object is to provide a self-test feature for apparatus controlled by a microprocessor. A further object is to provide a self-test procedure which utilizes a minor part of an existing ROM in a processor device.